| Re: Isolater vs Alternator [message #326640 is a reply to message #326629] |
Sat, 02 December 2017 10:57   |
Ken Burton
Messages: 10030
Registered: January 2004
Location: Hebron, Indiana
Karma:
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Some alternator regulators have a limit built in to them. I think it is set around 18 volts. On my airplane after I fixed the damage and replaced the external regulator, I added a crowbar circuit that fires an SCR and trips the field circuit breaker at around 15 volts. That shuts down the alternator. This would not work on a GMC because the regulator is internal to the alternator.
On a GMC I have often thought of adding 2 diodes in series giving a 1.3 or 1.4 volt drop. The diodes could go between output and the sense line input. Also 2 resistors could be used between the output and ground. Then tap the junction of the two and attach it to the sense line. The values could be 9 to 1 or 15 to 1 for a 10% to 15% voltage cap.
On the loose sense connection at the alternator. On mine the connection that was loose was actually on the added APC female terminal. So I am suggesting that even if you have an APC attached, that connection needs to be checked to be sure it is very very tight. That APC was on there for many years before the connection failed. I really felt stupid when I found it, because Colonel Ken had already twice run be back and forth to AZ for a replacement alternator.
When this problem popped up, I noticed it on my $2.00 volt meter while driving. I was able to manage the over voltage while driving buy adding load. I turned on the headlights and ran the heater fan at various speeds to keep the output at a reasonable voltage level. When I arrived at the rally a couple of days later I erroneously replaced the alternator under warranty and eventually found the loose sense connection. Without that meter I would not have been able to accomplish this.
Ken Burton - N9KB
76 Palm Beach
Hebron, Indiana
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